The crossed adductor reflex in humans: an EMG study.

Crossed adductor reflexes were recorded electromyographically in ten patients with bilateral lesions of the upper motor neuron. Three of these had a femoral neuropathy. Following blows directed to either the tendon of the adductor muscle or to the medial epicondyle of the femur, large amplitude responses of short latency and large amplitude responses of long latency were recorded from the contralateral adductor. The responses of short latency which were recorded from the ipsilateral and contralateral adductor muscles ranged from 18 to 27 ms. The contralateral responses of long latency ranged from 60 to 67 ms. On tapping the patella or patellar tendon, large amplitude responses of short latency were recorded from the contralateral adductor muscles while the ipsilateral adductor responses were absent. These responses resulted from stretch of the ipsilateral and contralateral adductor muscles. The contralateral responses were mediated across from the midline by an extraspinal mechanical pathway.